Modulus of a Complex Number

Consider the complex number $z = 3 - 4i$. To find the modulus of the complex number, use the formula for the modulus:

$$|z| = ext{sqrt}(a^2 + b^2)$$

where $a$ is the real part and $b$ is the imaginary part of the complex number $z = a + bi$. What is the modulus of the complex number $z = 3 - 4i$?